11.3KVIEWS
13REPLIES
3APPRECIATES
06-21-2018LAST POST
Hello -

My car went into limp mode the other night, got a reduced engine power idrive message, but no cel. Turned off and started again, no issue. Next day, went into limp mode 5 times over the course of 12 miles on the tail of the dragon, man was that a pain (good thing nobody else was following me). I read somewhere that it could be the brake vacuum sensor, but also saw one post saying it could be bad gas. I ran the tank dry, added a few gallons then ran dry again. Filled all the way and drove 250 miles with no issues. Figured it was the gas. Sure enough, tank is low again and I could barely drive 3 miles to work in limp mode and eventually got an SES light and an additional increased emissions idrive indication. I've ordered the brake vacuum sensor as that seems to be the solution, but my code reader shows two secondary messages as P1209 $07e8 and P1209 $07e8pd. What I'm wondering is what the $07e8 things refer to. However, I've also seen it tied to an injector control system pressure fault issue. What are my next steps to figuring out what the issue is? Could it be a fuel pump issue or clogged filter since it could be a fuel pressure issue? Car has 108k miles. Thanks.
Have you recently change your brake fluid?
msan wrote
Have you recently change your brake fluid?
I did, yes. I figured that's what the culprit was however I don't remember spilling fluid. Last night, I took off the reservoir and pulled out the sensor and the seal was a little beaten up and shredded. I put on some black rtv just as a band aid fix until my new sensor with vacuum piping comes in on Monday. After the rtv, only went into limp mode once in the same distance where it would do it five times.
FWIW, I had a low fuel-pressure sensor that was going bad and it threw all kinds of codes, including engine mis-firing which scared the crap out of me. I changed the plugs and did a few other things, come to find out it was just the low fuel-pressure sensor on the fuel rail that runs behind the air box on the fire wall. $97 shipped and 20min to fix. ATL Dealer wanted $1500 to replace it. It resolved the 4 or 5 different codes I got.
check back after replacing the brake vacuum sensor. May solve your issues.
thasuperdude wrote
FWIW, I had a low fuel-pressure sensor that was going bad and it threw all kinds of codes, including engine mis-firing which scared the crap out of me. I changed the plugs and did a few other things, come to find out it was just the low fuel-pressure sensor on the fuel rail that runs behind the air box on the fire wall. $97 shipped and 20min to fix. ATL Dealer wanted $1500 to replace it. It resolved the 4 or 5 different codes I got.
Part number?
msan wrote
Have you recently change your brake fluid?
is there a special procedure to change brake fluid on these cars? spilled fluid from reservoir known to cause these issues?
SFCM3 wrote
is there a special procedure to change brake fluid on these cars? spilled fluid from reservoir known to cause these issues?
No special procedure. Just don't spill any . Also be careful when spreading the calipers (when changing pads or rotors) as this can push fluid out of the brake fluid reservoir and make it drip down which will also kill the sensor.
msan wrote
No special procedure. Just don't spill any . Also be careful when spreading the calipers (when changing pads or rotors) as this can push fluid out of the brake fluid reservoir and make it drip down which will also kill the sensor.
Got it. usually the only time fluid spills out after spreading calipers is when people "top off" brake fluid...i keep trying to explain to people that if its low, your pads are probably worn out, but they continue to fill brake resv. :confused2
Vacuum sensor was the cause. Now fixed.